EP0086182B1 - Electronic impedance-matched line repeater - Google Patents

Electronic impedance-matched line repeater Download PDF

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Publication number
EP0086182B1
EP0086182B1 EP83850016A EP83850016A EP0086182B1 EP 0086182 B1 EP0086182 B1 EP 0086182B1 EP 83850016 A EP83850016 A EP 83850016A EP 83850016 A EP83850016 A EP 83850016A EP 0086182 B1 EP0086182 B1 EP 0086182B1
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EP
European Patent Office
Prior art keywords
wire
line
repeater
amplifier
impedance
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Expired
Application number
EP83850016A
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German (de)
French (fr)
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EP0086182A2 (en
EP0086182A3 (en
Inventor
Lars Anders Lenell
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Telefonaktiebolaget LM Ericsson AB
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Telefonaktiebolaget LM Ericsson AB
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Priority to AT83850016T priority Critical patent/ATE26782T1/en
Publication of EP0086182A2 publication Critical patent/EP0086182A2/en
Publication of EP0086182A3 publication Critical patent/EP0086182A3/en
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Publication of EP0086182B1 publication Critical patent/EP0086182B1/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M19/00—Current supply arrangements for telephone systems
    • H04M19/001—Current supply source at the exchanger providing current to substations
    • H04M19/005—Feeding arrangements without the use of line transformers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
    • H04B1/40—Circuits
    • H04B1/54—Circuits using the same frequency for two directions of communication
    • H04B1/58—Hybrid arrangements, i.e. arrangements for transition from single-path two-direction transmission to single-direction transmission on each of two paths or vice versa
    • H04B1/587—Hybrid arrangements, i.e. arrangements for transition from single-path two-direction transmission to single-direction transmission on each of two paths or vice versa using opto-couplers

Definitions

  • the present invention relates to an electronic impedance-matched line repeater for connecting a two-wire line to a subscriber exchange.
  • a line repeater has the task of forming a junction between a two-wire line (the two-wire side) and two four-wire sides with the object of subdividing the traffic flow through the line into two one-way paths, (see e.g. IBM Technical Disclosure Bulletin, vol. 16, no. 2, July 1973, pages 495 to 496).
  • external line repeaters i.e. such repeaters as are arranged between a subscriber exchange and an outgoing line (a line to the main station)
  • there is also desired a very well- defined AC impedance which is in most cases somewhat higher, seen from this side.
  • the object of the present invention is to provide an electronic line repeater, particularly an external line repeater, with impedance matching in respect of both AC and DC, as seen from the two-wire side.
  • a feed-back loop containing amplifier elements is arranged from the two-wire side of the repeater to the incoming four-wire side, whereby desired DC and AC impedance can be obtained by given values for the selected working point and for the gain of the amplifier elements incorporated in the feed-back loop.
  • the invention is characterized by the features set forth in the characterizing portion of claim 1.
  • the input terminal to the left forms the two-wire side of the repeater.
  • a voltage U 1 appears across this terminal which comprises a direct component (the supply direct voltage) and an alternating component (the speech signals from and out, respectively, the line).
  • the two-wire loop contains two resistors R 1 and R 2 having the same resistance, and constituting protective resistances to overvoltages.
  • a balanced line amplifier F2 contains a driving stage D which is an operational amplifier circuit and an LED light-emitting diode for galvanic isolation between the two- and four-wire sides, described in the European Patent Application No. 0086183 (published on 17.8.83).
  • the LED in the driving stage D is optically coupled to a phototransistor T, the collector-emitter circuit of which is connected to both resistors R1 and R2.
  • the phototransistor T can also be connected to a Darlington circuit comprising two transistors, as is illustrated in the application mentioned.
  • a feed-back loop is provided, comprising a differential amplifier circuit F1 and a resistor R.
  • the circuit F1 has two input pairs, of which one is connected across the input of the two-wire side and thus senses the potential drop U i , the other pair being connected to the output side of the balanced line amplifier F2 and thus senses the potential drop U 2 .
  • the four-wire side receiver and transmission paths contain buffer steps OP4 and OP5, respectively, suitably looped operational amplifiers of known design.
  • the receiver path buffer step OP4 is connected via the resistor R to the input of the line amplifier.
  • the incoming speech signal is denoted u s .
  • the following calculations are applicable for the line impedance matching in respect of DC and AC impedance matching.
  • the DC resistance on the two-wire side input (DC impedance) is determined by the resistance of the resistors R1 and R2 and also by the selected working point of the transistor T. Assume that the voltage U 2 has a direct component U o2 and that the working point of the transistor T is selected so that its collector-emitter current is ICE, then the DC impedance
  • the differential amplifier F1 is assumed to have very high-ohmic inputs and thus does not influence the value of Z dc . Since R 1 +R 2 are constant, the working point of the transistor T can be adjusted so that the desired value of U 02 /I CE is obtained. The transistor T must however operate in its linear range.
  • the desired input impedance can be obtained if the amplification F 1 and F 2 in the units F1 and F2, respectively, are selected so that correct negative feed-back gives the desired input impedance.
  • the amplification F 1 and F 2 in the units F1 and F2, respectively are selected so that correct negative feed-back gives the desired input impedance.
  • the input impedance Z AC for alternating current will thus be:

Abstract

An electronic line repeater for connecting a two-wire line to a subscriber exchange is impedance-matched to the two-wire side with the aid of a feedback circuit from the two-wire side of the repeater to the incoming four-wire side. The feedback includes a differential amplifier (F1) which senses the speech voltage drop on the two-wire side, and a resistor (R) connected to the line amplifier (F2) of the repeater. Impedance matching can be achieved by definite values of the gain provided by the differential amplifier and the line amplifier.

Description

    Technical field
  • The present invention relates to an electronic impedance-matched line repeater for connecting a two-wire line to a subscriber exchange.
    • Background art
  • A line repeater has the task of forming a junction between a two-wire line (the two-wire side) and two four-wire sides with the object of subdividing the traffic flow through the line into two one-way paths, (see e.g. IBM Technical Disclosure Bulletin, vol. 16, no. 2, July 1973, pages 495 to 496). Particularly with external line repeaters, i.e. such repeaters as are arranged between a subscriber exchange and an outgoing line (a line to the main station), it is desired to have as low-ohmic DC impedance as possible, seen from the line side (two-wire side). Furthermore, there is also desired a very well- defined AC impedance, which is in most cases somewhat higher, seen from this side. In known structures this impedance matching has been solved by accurate and relatively complicated dimensioning of hybrid transformers, e.g. according to the European Patent Application No. 0077351, published on 27.4.83. Impedance matching has been carried out in such cases with the aid of RC components in the hybrid transformer, the hybrid itself having been implemented in the form of a transformer coupling.
    • Disclosure of invention
  • The object of the present invention is to provide an electronic line repeater, particularly an external line repeater, with impedance matching in respect of both AC and DC, as seen from the two-wire side.
  • This object is achieved in accordance with the invention, such that a feed-back loop containing amplifier elements is arranged from the two-wire side of the repeater to the incoming four-wire side, whereby desired DC and AC impedance can be obtained by given values for the selected working point and for the gain of the amplifier elements incorporated in the feed-back loop. The invention is characterized by the features set forth in the characterizing portion of claim 1.
    • Brief description of drawing
  • The invention will now be described in detail while referring to the appended drawing, illustrating a circuit diagram of the line repeater in accordance with the invention.
    • Mode for carrying out the invention
  • In the circuit diagram of the Figure, the input terminal to the left forms the two-wire side of the repeater. A voltage U1 appears across this terminal which comprises a direct component (the supply direct voltage) and an alternating component (the speech signals from and out, respectively, the line). The two-wire loop contains two resistors R1 and R2 having the same resistance, and constituting protective resistances to overvoltages. A balanced line amplifier F2 contains a driving stage D which is an operational amplifier circuit and an LED light-emitting diode for galvanic isolation between the two- and four-wire sides, described in the European Patent Application No. 0086183 (published on 17.8.83). The LED in the driving stage D is optically coupled to a phototransistor T, the collector-emitter circuit of which is connected to both resistors R1 and R2. The phototransistor T can also be connected to a Darlington circuit comprising two transistors, as is illustrated in the application mentioned. In accordance with the invention, a feed-back loop is provided, comprising a differential amplifier circuit F1 and a resistor R. The circuit F1 has two input pairs, of which one is connected across the input of the two-wire side and thus senses the potential drop Ui, the other pair being connected to the output side of the balanced line amplifier F2 and thus senses the potential drop U2. The differential amplifier circuit F1 provides an output U3=F1 (U1―U2) and contains three operational amplifiers OP1 to OP3. Both amplifiers OP1 and OP2 sense the potential drops U1 and U2, respectively, and each transmits signals to both inputs of the amplifier OP3. This amplifier subtracts and filters the output signals from the amplifiers OP1, OP2 and gives the output signal u3, which does not contain any DC-component from the two-wire side but only the speech signal component, since a difference signal is formed in the amplifier OP3. The output signal from the amplifier OP3 thus constitutes an amplified speech signal from the two-wire side. This signal is connected via the resistor R to the input of the line amplifier F2.
  • The four-wire side receiver and transmission paths contain buffer steps OP4 and OP5, respectively, suitably looped operational amplifiers of known design. The receiver path buffer step OP4 is connected via the resistor R to the input of the line amplifier. The incoming speech signal is denoted us. If low-ohmic output is assumed for the buffer step OP5, as with the output of the final amplifier OP3 (which is the general case for operational amplifiers), the input signal U4 to the line amplifier F2 (which thus only contains the speech signal) is obtained by voltage division between the resistances of the resistors R, i.e. u4=u3/2+u5/2 if the resistors R have the same resistance. The following calculations are applicable for the line impedance matching in respect of DC and AC impedance matching.
    • DC impedance matching
  • The DC resistance on the two-wire side input (DC impedance) is determined by the resistance of the resistors R1 and R2 and also by the selected working point of the transistor T. Assume that the voltage U2 has a direct component Uo2 and that the working point of the transistor T is selected so that its collector-emitter current is ICE, then the DC impedance
    Figure imgb0001
  • The differential amplifier F1 is assumed to have very high-ohmic inputs and thus does not influence the value of Zdc. Since R1+R2 are constant, the working point of the transistor T can be adjusted so that the desired value of U02/ICE is obtained. The transistor T must however operate in its linear range.
    • AC impedance matching
  • From the circuit diagram it will be seen that the desired input impedance can be obtained if the amplification F1 and F2 in the units F1 and F2, respectively, are selected so that correct negative feed-back gives the desired input impedance. By superposition is obtained input impedance
    Figure imgb0002
  • From the block diagram it will be seen that the following equation relationships can be set up:
    Figure imgb0003
    Figure imgb0004
    Figure imgb0005
  • For the no-load state:
    • 1=0, U1=U2, which gives U3=0 and
    • u2=F2. U5/2, where u1, u2 denote the signal magnitudes of U1 and U2 respectively.
  • For short-circuiting:
    Figure imgb0006
    which gives
    Figure imgb0007
    and
    Figure imgb0008
    and
    Figure imgb0009
    so that
    Figure imgb0010
    i.e.
    Figure imgb0011
  • The input impedance ZAC for alternating current will thus be:
    Figure imgb0012
  • For example, if an AC impedance ZAc=600 ohms is desired and R1=R2=30 ohms, there is obtained according to the above that F1. Fz=18. Assume that F2=0,2 which is a usual value for the coupling factor of an optocoupler, there is obtained F1=90. This amplification of the block F1 is very moderate, and can be achieved without difficulty and be kept constant by suitably selecting the resistors determining the gain.
  • By introducing integrating or differentiating networks in a manner known per se, in the operational amplifier block F1, the gain F1 can be made complex, i.e. F1=F1(jw) whereby a complex ZAC may be obtained.

Claims (4)

1. Electronic impedance-matched line repeater included in a two-wire to four-wire converter for connecting a two-wire line to a telephone exchange including a two-wire side as well as an incoming and an outgoing four-wire side, the two-wire side of the repeater comprising an external line loop containing resistors (Ri, Rz) connected as overvoltage protection and a balanced line amplifier (F2), the output side of which is connected in series with said resistors (Ri, R2) and the input side of which forms one (incoming) four-wire path via a first resistor (R), characterized in that a feedback loop is provided for impedance matching to the two-wire line, and constitutes a differential amplifier circuit (F1) with two input pairs, of which one is connected directly to the two-wire input and the other is connected across the output side of the line amplifier (F2), the output of the differential amplifier (F1) being connected via a second resistor (R) to the input of the line amplifier (F2), and furthermore forms the second (outgoing) four-wire path.
2. Electronic line repeater as claimed in claim 1, characterized in that said differential amplifier (F1) has a low-ohmic output which, via the first and the second resistor (R) is connected to a low-ohmic output at one (incoming) four-wire side (OP4).
3. Electronic line repeater as claimed in claim 2, characterized in that said first and second resistors (R) have the same resistance.
4. Electronic line repeater as claimed in any of the claims 1 to 3, characterized in that the amplification of the differential amplifier (F1) is frequency-dependent, so that complex impedance-matching with the two-wire side is obtained.
EP83850016A 1982-02-09 1983-01-26 Electronic impedance-matched line repeater Expired EP0086182B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT83850016T ATE26782T1 (en) 1982-02-09 1983-01-26 ELECTRONIC LINE AMPLIFIER WITH IMPEDANCE ADJUSTMENT.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8200741A SE430198B (en) 1982-02-09 1982-02-09 ELECTRONIC IMPEDANCE CUSTOM LINE TRANSFER
SE8200741 1982-02-09

Publications (3)

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EP0086182A2 EP0086182A2 (en) 1983-08-17
EP0086182A3 EP0086182A3 (en) 1984-08-15
EP0086182B1 true EP0086182B1 (en) 1987-04-22

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EP83850016A Expired EP0086182B1 (en) 1982-02-09 1983-01-26 Electronic impedance-matched line repeater

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EP (1) EP0086182B1 (en)
AT (1) ATE26782T1 (en)
CA (1) CA1195446A (en)
DE (1) DE3371151D1 (en)
SE (1) SE430198B (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2898165B2 (en) * 1993-04-16 1999-05-31 シャープ株式会社 Hybrid circuit

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4181824A (en) * 1978-10-10 1980-01-01 Bell Telephone Laboratories, Incorporated Balancing impedance circuit
FR2462070A1 (en) * 1979-07-17 1981-02-06 Cit Alcatel DEVICE FOR SUPPLYING A SUBSCRIBER STATION

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
IBM TECHNICAL DISCLOSURE BULLETIN, vol. 16, no. 4, September 1973, pages 1173-1174, New York, USA M.A. PATTEN: "Electronic hybrid telephone line pack" *

Also Published As

Publication number Publication date
EP0086182A2 (en) 1983-08-17
SE8200741L (en) 1983-08-10
CA1195446A (en) 1985-10-15
SE430198B (en) 1983-10-24
DE3371151D1 (en) 1987-05-27
ATE26782T1 (en) 1987-05-15
EP0086182A3 (en) 1984-08-15

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